#!/usr/bin/python
# -*- coding: UTF-8 -*-
class MyNumber():
    def __iter__(self):
        self.a =1
        return self
    def __next__(self):
        if self.a <= 20:
            x = self.a
            self.a += 1
            return x
        else:
            raise StopIteration
myclass = MyNumber()
myiter = iter(myclass)
for i in myiter:
    print(i)